Since then he has impressed on loan at Birmingham, has scored five in 17 for the Hammers this term and could even be in line for a shock call-up to Roy Hodgson’s World Cup squad.

Allardyce added: “Sir Alex let Ravel go for his own benefit. He said that if Ravel’s going to be a player he has to leave Manchester and go somewhere else in this country because he felt being in Manchester wasn’t helping him develop.

“[He said] if he comes down to you hopefully he’ll find a new life and a new way of living and then his performances and his ability will then start to come through.

“In actual fact, he struggled to look like he was capable of playing football in the first team with us. That’s why we sent him on loan to Birmingham and I thought since that year he’s grown up.

“Somewhere along the line lads wake up and they start coming in and thinking, ‘I can have all the help I need but if I don’t change myself then I’m not going to be successful’. I think he’s changed himself and delivered.”

Morrison has about 18 months left on his current agreement and it has been suggested the east London club are lining up a bumper new deal for the England Under-21 midfielder.

But Allardyce has told him that if he keeps concentrating on ­football then “mega-bucks” will come his way.

The Hammers manager, who will be without suspended skipper Kevin Nolan at Old Trafford on Saturday , said: “A lot of the time, too often, it revolves around money and not football. But it should revolve around having a good career and then money follows.

“If it ends up in the Premier League then it’s mega-bucks. If you don’t get there and you take the money then the career can stagnate on that basis.”

Morrison is fresh after sitting out West Ham’s Capital One Cup quarter-final win over Tottenham on Wednesday – and is expected to start against David Moyes’ side, who are hoping to avoid a third straight home defeat in the Premier League.